Human fibroblast cell cultures from biopsies of manic depressive patients, their family members, and normal controls are established to study lithium ion transport and kinetics. Inhibitors of specific transport mechanisms, ouabain and phloretin, are used to determine transport defects in cells showing abnormal lithium incorporation. Abnormal kinetic effects on monamine metabolism are studied by assaying for monamine oxidase. Cell membrane and toxicity effects of long-term exposure are also examined.